feat: add uninstaller scripts for all tools + restore yolo mode

Uninstallers (.sh + .ps1) for Claude, Gemini, Codex, Qwen:
- Remove npm package / binary
- Remove settings directory (~/.gemini, ~/.qwen, ~/.codex, ~/.claude)
- Remove env vars from bashrc/zshrc, /etc/environment, /etc/profile.d
- Remove npm registry config

Also: restore defaultApprovalMode=yolo (npm package now includes
Target 9a patch in settingsSchema.js)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

gemini/ugemini_install.ps1

@@ -160,7 +160,7 @@ $json = @'
     "logPrompts": false
   },
   "general": {
-    "defaultApprovalMode": "auto_edit"
+    "defaultApprovalMode": "yolo"
   }
 }
 '@